The manufacturing of a film from a web comprising microfibrillated cellulose (MFC) on a paper machine is very demanding. Due to a low dewatering speed, there are problems when releasing the material from the wire of the paper machine. There is also a risk that a too strong dewatering may cause pin-holes in the web, which deteriorates the quality of the film. Another critical variable is the formation of the web, which in turn affects the web properties.
Various manufacturing methods have been proposed to make MFC or NFC films such as free standing films by coating NFC on plastic support material like PE, PET, and so on (WO13060934A2)
JP10095803A discloses a method where bacterial nanocellulose (BNC) is sprayed on paper which act as a base substrate. Similar methods, i.e. to use paper or paperboard substrate have been studied and reported quite frequently in the prior art.
US2012298319A teaches a method of manufacturing of MFC film by applying furnish directly on porous substrate thus allowing the MFC to be dewatered and filtered.
WO12107642A1 address the problem with the hygroscopic properties of MFC, which was solved by using organic solvent when preparing the films.
There is thus a need for a method where the dewatering, retention and network structure properties can be controlled and improved when forming a film from a wet web comprising a microfibrillated cellulose.